5.2. Scheduling Terms

Making sure all stakeholders use the same terminology is crucial in all phases of project management, but it’s especially important when you are trying to get a group of diverse people to agree to a schedule. After all, a schedule only works as a form of communication if it is written in a language everyone understands. And since contract terms are often tied to a schedule, a lack of common agreement on the meaning of specific terms in a schedule can have far-ranging effects.

Terminology is so important that many state governments around the United States publish their own project management glossaries. As you embark on a new project, you’d be wise to find out if the organization you work for, or the vendors you will be working with, have compiled such a glossary. If such organizational resources exist, use them as a starting point for your own project glossary. Otherwise, you can always turn to the Project Management Institute’s lexicon (available here: “PMI Lexicon of Project Management Terms”) or glossaries provided online by consulting firms or other project management resources such as the following:

The following definitions of scheduling-related terms are taken from a variety of sources.

  • milestone: “A significant event in the project; usually completion of a major deliverable” (State of Michigan: Department of Technology, Management & Budget, 2013, p. 13). An important distinction is that a milestone is a zero-duration activity; e.g., “acceptance of software by client” is a milestone, preceded by many contributing activities.
  • activity: “An element of work performed during the course of a project. An activity normally has an expected duration, an expected cost, and expected resource requirements” (Project-Management.com, 2016). Beware that some organizations subdivide activities into tasks while others use task and activity synonymously.
  • duration: “The amount of time to complete a specific task given other commitments, work, vacations, etc. Usually expressed as workdays or workweeks” (State of Michigan: Department of Technology, Management & Budget, 2013, p. 9).
  • resource: “Any personnel, material, or equipment required for the performance of an activity” (Project-Management.com, 2016).
  • cost: “An expenditure, usually of money, for the purchase of goods or services” (Law, 2016).
  • slack: “Calculated time span during which an event has to occur within the logical and imposed constraints of the network, without affecting the total project duration” (Project-Management.com, 2016). Put more simply, slack, which is also called float, is the amount of time that a task can be delayed without causing a delay to subsequent tasks or the project’s overall completion date.

7. Project Scheduling” from Technical Project Management in Living and Geometric Order, 3rd edition by Jeffrey Russell, Wayne Pferdehirt and John Nelson  is licensed under a Creative Commons Attribution 4.0 International License.


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